Jourdan-Pineau Hélène, Dupont-Prinet Aurélie, Claireaux Guy, McKenzie David J
Centre d'Ecologie Fonctionnelle et Evolutive (Unité Mixte de Recherche [UMR] 5171 Centre National de la Recherche Scientifique [CNRS]), 34293 Montpellier Cedex 5, France.
Physiol Biochem Zool. 2010 Jan-Feb;83(1):68-77. doi: 10.1086/648485.
We investigated the ability of European sea bass (Dicentrarchus labrax) to respond simultaneously to the metabolic demands of specific dynamic action (SDA) and aerobic exercise and how this was influenced by moderate hypoxia (50% air saturation). At 3 h after feeding in normoxia at 20 degrees C, SDA raised the instantaneous oxygen uptake (Mo(2)) of sea bass by 47% +/- 18% (mean +/- SEM, N = 7) above their standard metabolic rate (SMR) when fasted. This metabolic load was sustained throughout an incremental exercise protocol until fatigue, with a 14% +/- 3% increase in their maximum aerobic metabolic rate (MMR) relative to their fasted rate. Their incremental critical swimming speed (U(crit)) did not differ between fasted and fed states. Thus, in normoxia, the bass were able to meet the combined oxygen demands of SDA and aerobic exercise. In hypoxia, the sea bass suffered a significant decline in MMR and U(crit) relative to their normoxic performance. The SDA response was similar to normoxia (84% +/- 24% above fasted SMR at 3 h after feeding), but although this load was sustained at low swimming speeds, it gradually disappeared as swimming speed increased. As a result, the hypoxic sea bass exhibited no difference in their fasted versus fed MMR. Hypoxic U(crit) did not, however, differ between fasted and fed states, indicating that the sea bass deferred their SDA to maintain exercise performance. The results demonstrate that, in normoxia, the sea bass possesses excess cardiorespiratory capacity beyond that required for maximal aerobic exercise. The excess capacity is lost when oxygen availability is limited in hypoxia, and, under these conditions, the sea bass prioritize exercise performance. Thus, environmental conditions (oxygen availability) had a significant effect on patterns of oxygen allocation in sea bass and revealed intrinsic prioritization among conflicting metabolic demands.
我们研究了欧洲海鲈（Dicentrarchus labrax）同时应对特定动力作用（SDA）的代谢需求和有氧运动的能力，以及这如何受到中度缺氧（50%空气饱和度）的影响。在20摄氏度常氧条件下喂食后3小时，SDA使海鲈的瞬时耗氧量（Mo(2)）比禁食时的标准代谢率（SMR）提高了47%±18%（平均值±标准误，N = 7）。在递增运动方案直至疲劳的整个过程中，这种代谢负荷一直持续，其最大有氧代谢率（MMR）相对于禁食时的速率增加了14%±3%。它们的递增临界游泳速度（U(crit)）在禁食和喂食状态之间没有差异。因此，在常氧条件下，鲈鱼能够满足SDA和有氧运动的综合氧气需求。在缺氧条件下，相对于它们在常氧条件下的表现，海鲈的MMR和U(crit)显著下降。SDA反应与常氧条件下相似（喂食后3小时比禁食时的SMR高84%±24%），但尽管这种负荷在低游泳速度下持续存在，但随着游泳速度增加它逐渐消失。结果，缺氧的海鲈在禁食和喂食时的MMR没有差异。然而，缺氧时的U(crit)在禁食和喂食状态之间没有差异，这表明海鲈推迟了它们的SDA以维持运动表现。结果表明，在常氧条件下，海鲈拥有超出最大有氧运动所需的额外心肺能力。当缺氧时氧气供应有限时，这种额外能力丧失，并且在这些条件下，海鲈优先考虑运动表现。因此，环境条件（氧气供应）对海鲈的氧气分配模式有显著影响，并揭示了相互冲突的代谢需求之间的内在优先级。
